1. Field of the Invention
The present invention relates to a check valve device which makes it possible to flow a pressure fluid in only one direction through a fluid passage and which makes it possible to prevent the pressure fluid from flowing in the opposite direction.
2. Description of the Related Art
A check valve is used for flowing a pressure fluid in only one direction and preventing the pressure fluid from flowing in the opposite direction in a fluid circuit.
FIG. 7 shows such a conventional check valve. The check valve 1 includes a body 2 and a cover 3 which are connected to form a substantially cylindrical shape, and a seat ring 4 interposed at the connecting portion between the body 2 and the cover 3.
The check valve 1 further includes a seat section 5 of a rubber material covering the seat ring 4, a valve plug 6 which is capable of being seated on the seat section 5, a spring-receiving member 7 contacting the valve plug 6 and provided slidably along the inner wall surface of the body 2, and a spring member 8 of metal for pressing the valve plug 6 against the seat section 5 by being fastened by the spring-receiving member 7.
An explanation will be made briefly about the operation of the conventional check valve 1. The pressure fluid inflowing from a first port 9a in the cover 3 presses the valve plug 6 in the right direction in FIG. 7. The valve plug 6 is displaced against the spring force of the spring member 8 by the pressure fluid, and thus the valve plug 6 is separated from the seat section 5 in the valve-opened state. Therefore, the pressure fluid inflowing from the first port 9a in the cover 3 passes through the gap between the seat section 5 and the valve plug 6, and the pressure fluid outflows from a second port 9b disposed in the body 2.
When the pressure fluid inflows from the second port 9b disposed in the body 2 reversely to the above, the pressure fluid presses the valve plug 6 against the seat section 5. Therefore, the pressure fluid is prevented from flowing from the second port 9b in the body 2 toward the first port 9a in the cover 3.
For example, when the conventional check valve as described above is incorporated into a semiconductor manufacturing apparatus through which liquid chemical or the like flows, some iron rust or the like may appear, or some harmful influence may be exerted on the component of the flowing liquid chemical. This is because the spring member made of metal is exposed in the passage.